Previous post on nautical cleric spells got me thinking about nautical wilderness adventures. It turns out that seafaring adventures address my concerns about attrition in the wilderness by adding a new resource which is non-recoverable in the field: the ship's HP. "Only half of all damage sustained by a ship can be repaired at sea by the crew. The remaining damage can only be repaired by facilities at dock." Such partial-recovery rules would be annoying to track for all the PCs and henchmen, but seem pretty viable when the party has only one ship.
Incidentally, re-reading the ship combat rules, it turns out that those giant catfish last campaign should've dealt a lot less damage to the party's canoes, because "giant sea monsters and magical attacks do 1 structural HP of damage for every 5 points of damage their attack normally does". I regret nothing; that would've been a very boring fight without the risk of sinking (I suppose I could've made it about risk of capsizing / being tipped out of the boat). Knowing that ships are five times as durable as we thought, however, might encourage their use.